Staying awake

During the events that went down in the mine, I found myself asking how long a character might remain awake and competent under strenuous activity in the face of exhaustion from lack of sleep? I haven't found any official rules on this yet, though it's possible that something already exists. In lieu of that, I've devised a quick system to employ if the situation ever comes up again. I don't expect this to be at all commonplace, though it seems like when it happens, it's likely very important.

• A character or NPC can stay awake at full capabilities for a number of hours equal to 12 + Con score + 1d6.

• After this point, each of the individual's six ability scores are temporarily halved (rounding down, hit points unaffected) every hour. Whenever any score reaches zero (0), the individual passes out.

• A person passed out from exhaustion cannot be wakened for 1d8+8 hours, at which point they rise with scores restored to their normal values.

This all feels reasonable to me. Adrenaline lets you go as hard as you can for as long as you can, but at some point you hit the wall. When that happens, your ability to function drops off quickly. You can still manage to push for up to a few hours longer, but eventually either your mind or body gives out.